The present invention relates in general to communication systems and components therefor, and is particularly directed to an automated, processor-controlled mechanism for periodically testing the xe2x80x98healthxe2x80x99 of a back-up or auxiliary battery, that is used to supply power to an electrically powered system, such as that employing telecommunication equipment, in the event of a failure of the equipment""s primary power source, and for generating at least one alarm indication if testing of the battery determines that the back-up battery has failed.
Various system equipment providers, such as, but not limited to industrial, medical, communication and military equipment suppliers, often employ battery back-up for their deployed systems, in order to reduce the risk of loss of service to users/customers in the event of a failure of the equipment""s principal power source. Typically, the operation of a system provider""s equipment and primary power source are such that a back-up battery 10 (or batteries) remains charged and in a xe2x80x98floatingxe2x80x99 state for long periods of time, as the need for battery back-up is hopefully a relatively infrequent occurrence. As a result of some battery failure mechanisms and the long periods between uses, the failure of a back-up battery may not be detected until its use is actually required. This may lead to the failure of equipment through which the customer/user is expecting uninterrupted service.
In accordance with the present invention, this undetected battery failure problem is remedied by employing a cost-efficient, processor-controlled mechanism that is operative to periodically test the back-up battery, without compromising the availability of the back-up battery for its intended purpose, and to provide an alarm indication should the back-up battery be determined to be in a failed condition. As will be described, the battery test mechanism of the invention employs an interconnected arrangement of voltage and current monitoring circuits, an isolating relay, an internal fixed current test load, and a microcontroller, to implement a battery diagnostic algorithm for testing the battery at regular intervals. If a battery failure is detected, audible, visible, and electronic alarms are activated.
The test sequence executed by the invention tests the backup battery by isolating the battery from its input voltage source, and then applies a prescribed load across the battery for a given time interval, in order to draw a fixed current from the battery. A voltage associated with this current drain is monitored for the presence of an excessive battery voltage drop. If an excessive voltage drop is detected, it is inferred that the battery has failed.
Because a discharged battery (such as a lead acid battery) may have similar characteristics to an old or failed battery, battery charging current is monitored to ensure that the battery is charged, and thereby properly distinguish between a good battery that has simply been discharged and an expired battery that needs to be replaced. When the battery performance test is commanded and battery charging current is detected, a timer is set to bound the maximum time allowed for charging the battery. At the end of the this maximum time interval, should the level of battery charging current still be above the designated threshold, a failed battery is indicated. However, if, prior to expiration of the maximum charge time, the charging current falls below the charge current threshold value, it is inferred that charging of the battery is effectively complete, and a battery performance test may be conducted. The battery is then isolated from the primary voltage source and a battery load test is performed.
At the outset of the battery performance test sequence, if discharge current is detected, it is inferred that the power system with which the battery is used has been placed in battery backup mode; testing of the battery (via the isolation and load sequence described above) is immediately deferred pending battery test availability (that is, when the battery is no longer discharging as a back-up power source and has completed recharging). During its performance test, once it has been isolated from the input source, the back-up battery is no longer available to back up the primary power source. To accommodate the potential need for immediate battery back-up, the primary input voltage is monitored during the battery performance test; if the primary source""s voltage falls out of range, the back-up battery test is terminated and the battery is reconnected to the source. This operation occurs fast enough to prevent an interruption of power to the equipment.